He debuted professionally in 1983 with the Idaho Falls A's, hitting .163/~.198/.239. The hefty backstop struck out in 34 of his 92 AB. He moved on to the GCL Blue Jays in 1984 and batted .220/~.258/.257. Rojas led Gulf Coast League catchers that year in games (53), putouts (319), assists (55) and errors (9).

In 2004, Rojas managed the Oneonta Tigers, and he spent the next two years as skipper of the Lakeland Tigers. He was slated to become the Detroit Tigers' minor league catching coordinator in 2007 but instead spent the season as manager of the Toledo Mud Hens while Larry Parrish was recovering from ankle surgery. After the season, Rojas was promoted to Minor League Field Coordinator for the Tigers. IN 2011, Rojas was the Tigers' Director of player development. In July 2011, Jeff Jones was moved from bullpen coach to pitching coach, and Rojas replaced him as bullpen coach. He stayed in the position until the end of the 2013 season, then moved to the Seattle Mariners as bullpen coach in 2014, when fellow Tigers coach Lloyd McClendon was appointed as Seattle's manager.